FIELD OF THE INVENTION
The present invention relates to a means and methods for elevating structures, and in particular, to poles anchored in the ground for vertically elevating any type of member or members to an extended distance.
A number of structures or things must be suspended from the ground. Examples are light fixtures, sirens, antennas, wires, and the like. Many times these structures need to be rigidly supported. Of course, a conventional means to accomplish this is to utilize an elongated pole.
Commonly known examples of poles of this type are telephone poles, electrical wire poles, light poles, sign poles, and utility poles. Most of these types of poles are anchored in the ground and extend vertically upward to many times tens of feet in height.
The widespread utilization of these types of poles is indicative of the preference to utilize elongated structures or poles to elevate objects in the air. For whatever reasons, whether it be economical or practical, the demand for the poles is very high for a number of different uses.
Poles of this nature can be made of a number of materials and can be erected and installed in a number of ways. While each of the commonly used poles achieves the end result of elevating objects in the air, the different types commonly used have both their advantages and disadvantages.
Wood poles represent the longest used and still today the many times preferred type of pole. They are relatively inexpensive, have a good height to diameter strength ratio, and can be rather easily adapted for a number of uses.
Problems and disadvantages of wood poles, however, are at least:
a. Difficult to find straight wood poles, especially for taller heights; PA1 b. Natural processes decay or at least weaken wood; PA1 c. Wood is fairly heavy; PA1 d. Pole comes in single long length which can be difficult to transport; PA1 e. Environmental problems associated with using trees could effect availability; PA1 f. Appearance; PA1 g. Uncertainty of strength; and PA1 h. Bottom end is buried in the ground and therefore even more susceptible to decay and deterioration. Wood, therefore, may represent a cheaper, more available source for at least shorter poles, but is not the preferred type of pole because of, in significant part, some of the above mentioned problems. PA1 a. Very heavy, even with a hollow core (may not be able to make very long); PA1 b. Require a big crane or other power means to lift them; PA1 c. The weight tends to cause them to shift when positioned in the ground; PA1 d. It is somewhat difficult to form holes or otherwise attach structures to such poles; and PA1 e. Such poles present shipping problems due to weight, length, and width. PA1 a. Most expensive; PA1 b. Concrete and re-bar (if used) must be custom designed; PA1 c. Heavy, thick base plate must be welded to the lightweight steel tube; PA1 d. Galvanizing, which is the preferred protective coating, is sensitive to the temperature differences between the thick base and thin tube; PA1 e. Concrete foundations must be accurately constructed on the site according to the custom design; PA1 f. The poles and the concrete fill, and any other hardware many times are required to come from different sources and therefore may not adequately match; and PA1 g. Corrosion problems.
An alternative pole that has more recently been utilized is one made substantially of concrete. For even significantly tall poles, concrete has great strength in compression and with a steel cable infra structure offers strength in tension. With advances in the nature of concrete, such poles offer a relatively economical and very strong alternative to wood.
Disadvantages of concrete are at least the following, however:
Again, while concrete poles do provide some advantages, their disadvantages prevent them from being the preferred used type of pole.
These types of above-mentioned deficiencies have resulted in the pole of preference being comprised of a steel pole which is anchored in the ground usually to poured concrete fill. Such a combination allows the use of high strength yet lightweight hollow tube steel for the above ground portion, while utilizing lower cost and high weight concrete as the anchor in the ground. This also aids in installation as the concrete bases can be poured and then the lightweight steel poles mounted thereon.
These advantages do not come without a price however. The disadvantages of this type of pole are at least the following:
As can be appreciated, the problems with steel and concrete foundation poles are not insignificant. Because the joint between the steel and concrete will have to take much of the stress provided by the long moment arm of the upwardly extending pole, and because of wind load and other factors, it is critical that for each installation the junction between the pole and the foundation be accurately and correctly prepared. This is an intricate matter requiring not only the correct design specifications and construction of the concrete foundation and the steel pole, but also accurate and faithful adherence to design and installation specifications by field personnel in forming the concrete foundation.
The custom design must include not only the height and weight requirements associated with each particular pole, but also must consider the type and strength of concrete used, the design of the re-bar cage in the concrete, and the design and placement of hardware attaching the steel pole to the concrete.
As is well understood by those with ordinary skill in the art, a custom design for the concrete foundations requires significant expenditure of resources. Additionally, the success of the design is then entirely dependent upon its implementation in the field.
Unfortunately, a significant and real problem exists in contractors carrying out the installations not doing so accurately. Without a reliable match between the design parameters of the concrete foundation and the parameters associated with the steel pole with its actual installation, the entire pole structure is susceptible to damage or failure. Accordingly, substantial expense may be incurred over designing and installing the concrete foundations to allow for field installation tolerances. Additionally, concrete requires up to 28 days to develop full strength needed for strength and to anchor the bolts used to secure the pole.
A second major problem with steel pole and concrete foundation combinations is that of corrosion. While presently the corrosion problems are addressed by attempting to galvanize all metal components, at least the following impediments exist to that being successful.
The best environment for corrosion is generally within a few feet above and below the ground line. Most concrete and steel poles such as described above have the concrete bases foundations poured and submerged from ground level down. Therefore, the most corrosion-susceptible area of the metal, at or near the joint with the concrete, is in that area where corrosion is the most likely. Moisture in the form of standing water and condensation is most concentrated in this area. Additionally, this is also an area where the concentration of oxygen is high, which is one of the components of corrosion and rust.
Secondly, as previously mentioned, the joint between the steel pole and the concrete foundation often represents the highest stress area for the combination. It is known in the art that corrosion increases with stress.
Third, the conventional way of securing the joint is to utilize long bolts through a mounting plate of the steel pole into the concrete. These bolts also take a majority of the stress and are therefore very susceptible to corrosion.
Fourth, galvanizing simply cannot be very reliable for the following reasons. Stress is detrimental to galvanization. An annular base plate for the metal pole must be welded to the tubular elongated portion of the pole. For galvanization to be reliable, the surface must be extremely clean. Debris or dirt in general, and in particular flux, which is hard to remove around welded joints, will not take galvanization. Sometimes direct-bury steel poles are utilized. Corrosion problems as well as installation problems similar to described above exist.
Additionally, galvanization is accomplished by heating the metal. For reliable galvanization, the metal must be heated uniformly. However, the baseplate must be made of a much thicker metal than the thin tubular pole on a practical commercial scale. It is almost difficult during a reasonable production time to have a thick-in-cross-section metal portion connected to a thin-in-cross-section metal portion have the same temperature when exposed to heat.
Additionally, the chemical nature of the steel or metal must be known to obtain the correct galvanization result. Heat differences can even crack the weld or otherwise damage the joint or pole. The plate is generally made of a different metal than the pole.
In short, the mounting plate and metal pole must be galvanized inside and out to resist corrosion. For at least the above reasons, it is very difficult to get such a combination correctly galvanized. At a minimum, it is very expensive to do it right. Then, even once galvanized, the high stress in the area is damaging to the galvanization. Another risk is to cracking of the weld because of different thickness of metal.
It can therefore be seen that the conventional types of poles simply have significant and real problems which are detrimental or are disadvantageous. There is a real need in the art for a pole system which does not have these problems.
Additional problems with regard to presently used poles are also significant in the art. One very practical and real problem is involved with the shipping of such poles. For many uses, poles are needed of lengths of thirty, forty, and even up to over 100 feet. While some applications require many poles of similar lengths, and therefore may be sent by rail shipment, where long lengths can probably be accommodated, many applications for such poles require only a relatively small number. To ship such a number by rail is expensive, particularly when many of these applications still require some other type of over-the-highway transportation to the ultimate location.
Generally trucks have a maximum effective carrying length of between 40 and 48 feet, at least, for semi-trailers. However, the effective load carrying length generally is no longer than around 48 feet. Therefore, it is simply not possible to ship poles of much longer length than this via tractor trailer without special and expensive permits.
While attempts have been made to produce concrete poles in segments, this requires significant installation efforts and joints would create risk and problems. Additionally, it must be understood that wood and concrete poles, with their heavy weight, present shipping problems. Even with shipment in tractor trailers, there is a weight limit of approximately 45 thousand pounds, even for the longest semi-trailers. This would limit the number of such poles that could be transported in one truck as some poles, such as concrete, can each weigh several thousand pounds, and even around or over ten-thousand pounds. Additionally, weight permits are required for increasingly heavy loads. Thus, the closer you come to the maximum weight per trailer and truck, the more costs are incurred in obtaining permits and the like for such heavy loads. This is important because optimally the goal would be to have one tractor trailer carry all the poles and parts required for one installation. Because of limit on truck length and load weight limits, concrete and even wood poles have certain limitations.
Still further, for steel poles which are installed with conventional poured concrete foundations, it may be possible to transport the poles in trucks, but a disadvantage is again the requirement that the concrete foundations be created and installed by a local contractor where, in most cases, quality control is less reliable. In other words, the entire combination (pole and foundation) cannot be manufactured and shipped as one unitary shipment and much reliance on a successful installation is with the installer at the site.
The above rather detailed discussion of conventional poles is set forth to attempt to aid in an understanding of the many factors which are involved in choosing a type of pole, manufacturing it, installing it, and ultimately maintaining it for an extended, economical, and effective useful life. There is no presently satisfactory system which is adaptable to virtually every situation, is flexible in that it can be anchored in all sorts of locations and ground types and all sorts of weather environments, and is useful for all sorts of heights, wind loads, and types of structures to be elevated.
Still further, for purposes of economy, there is a real need for a pole system which can be easily shipped, whether only a few or quite a few; is easy in terms of labor and resources to install; and which can be maintained over a long life span.
Finally, there is a real need for an efficient pole system which allows easy installation and shipment of the entire system together, along with the structure or structures to be elevated and any attendant hardware, such as wiring and the like.
It is therefore a principle object of the present invention to provide a means and method for rigidly elevating a structure which improves over or solves the deficiencies and problems in the art.
Another object of the present invention is to provide a means and method as above described which is generally universal in its application for elevating different structures to different heights for different situations, and with respect to different installations of the base in the ground.
A still further object of the present invention is to provide a means and method as above described which is economical in terms of the manufacture, materials, transportation, installation, labor, and life span.
Another object of the present invention is to provide a means and method as above described which is easy to assemble, install, and maintain.
A still further object of the present invention is to provide a means and method as above described which is durable and strong, both in its individual components and compositely.
Another object of the present invention is to provide a means and method as above described which permits pre-installation design and concurrent shipment of all or most components for each installation.
A further object of the present invention is to provide a means and method as above described which improves corrosion resistance.
Another object of the present invention is to provide a means and method as above described which is an improvement with respect to the problems caused by stress.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.